The United States dropped laser-guided bombs on ISIS artillery in Iraq on Friday, kicking off airstrikes threatened a day earlier by President Obama, the Pentagon said. Two FA-18 jets dropped two 500-pound bombs on Islamic State of Iraq and al-Sham (ISIS) forces outside Erbil, the Kurdish capital, U.S. officials told NBC News. Obama said Thursday evening that he had authorized "targeted airstrikes" to protect U.S. interests in Iraq. The U.S. also launched an operation to drop humanitarian supplies of food and water to 40,000 members of the Yazidi religious sect, who are trapped on a mountaintop under the threat of mass execution by ISIS militants. Obama said that U.S. ground troops won't be returning to the besieged country.